The present invention concerns a device for providing the cross-section of the radiation emitted by several solid-state and/or semiconductor diode lasers and especially by arrays of such lasers, as recited in the preamble to claim 1 with a specific geometry.
Such a device is known from U.S. Pat. No. 4,978,197. Several lasers are distributed in rows, one behind another paralleling the X axis. Viewed as a linear arrangement of sources of radiation extending parallel to the X axis, the individual laser beams strike mirrors mutually displaced paralleling the X axis and associated with them. The individual beams are diverted to the mirrors, forwarded to a polarizing beam divider, and diverted again. The radiation from the second linear arrangement is again reflected onto prismatic mirrors in accordance with the first linear arrangement and forwarded to a deflecting mirror, combining the beams in the beam divider at its semitransparent reflecting surface with the separate radiation components from the first linear arrangement. Producing compound beams out of the components.
Their high efficiency and small size make diode lasers particularly interesting, even though the output of each laser is limited to a few hundred mW. That output can be increased, however, by combining several lasers into an emitter group at the laser's positive-to-negative junction. Such a group can comprise 20 lasers and can output a few watts. The output can be increased even farther by combining several adjacent groups into a strip, typically 10 mm long, at the positive-to-negative junction. Strips of individual diode lasers can output some tens of watts.
Still, outputs of more than a few hundred watts are necessary for some applications, in materials processing for example, where several strips need to be stacked parallel to the Y axis into "arrays". Such an array is schematically illustrated in FIG. 2, which will be discussed hereinafter in detail in the specification.
A serious problem that accompanies the extension of diode-laser outputs is that of the severe heat that occurs. The heat must be eliminated by providing the diodes with heat sinks. On the other hand, massive heat sinks, large enough cooling devices in other words, prevent the diodes or their radiation-emitting surfaces from being stacked close enough together to achieve the desired outputs. It is accordingly conventional to use thin slabs, typically 1 to 1.5 mm thick, for the heat sinks. Such thin slabs, however, not only do not absorb enough heat but are also not very thermally or mechanically stable, and produce considerable errors. The beam direction cannot be well enough defined.
Another consequence of thin heat sinks is the need to adhere to narrow tolerances. Even slight deviations from tolerance will lead to errors in directing the reflected beam that are very difficult to correct with downstream optical devices.
Still another problem is how to seal the stacked strips and thin heat sinks from the water employed as a coolant while simultaneously maintaining the supply of electrical power and without detriment to reflecting the radiation arriving from the individual diodes.
Finally, when an individual strip fails and a whole array has to be dismantled to allow access to it, the entire downstream optical system must be readjusted.
The aforesaid drawbacks, especially those associated with conventional arrays, make the components impractical for specific applications, fiber-optical connections for example, where the divergence must be collimated in the Y direction. Some state-of-the-art approaches employ complicated and expensive optics to align the rays from individual strips or arrays. Such systems, however, result in fields of radiation with intensities that cannot be distributed accurately perpendicular to the angle of propagation.